Effects of age and breed on corneal thickness, density, and morphology of corneal endothelial cells in enucleated sheep eyes

Objective The purpose of the study was to determine corneal thickness (CT), endothelial cell density (ECD), morphology, and morphometry in ovine eyes, and to report the effects of age and breed on these parameters. Animals studied and procedures Forty-eight healthy ovine eyes were classified into six groups (eight eyes per group) according to animals' age (lambs and adults) and breed (Manchega, Ripollesa, and Rasa Aragonesa). Endothelial cell density (cells/mm(2)) and CT (mu m) were calculated in the central cornea and four peripheral quadrants by means of specular microscopy. Mean cell area (MCA (mu m(2))), pleomorphism (% hexagonal cells), and polymegethism (CV) were evaluated in the central cornea. Statistics consisted of an ANOVA model and a LSD test for the post hoc analysis. Results Results in lambs were as follows: ECD = 3532 +/- 259, CT = 699 +/- 56, MCA = 283 +/- 22, % hexagonal cells = 75.64 +/- 3.09, and CV = 18 +/- 8.4; and in adults: ECD = 2204 +/- 261, CT = 804 +/- 87, MCA = 473 +/- 53, % hexagonal cells = 69.9 +/- 3.42, and CV = 18.1 +/- 5.2. There were differences (P < 0.001) in all parameters studied between both groups except for the CV (P = 0.962). Regarding the breed, Rasa Aragonesa presented a higher CT (P = 0.001) and CV (P = 0.04) compared to other breeds. Mean values of all groups together showed that central and dorsal areas of the cornea were the thickest, whereas temporal quadrant was the thinnest (P < 0.001). Conclusions This study demonstrates that age and breed influence corneal and endothelial parameters in sheep.